Heretofore, valves used to control the flow of gasoline from one of two tanks were solenoid operated. Such arrangements were controlled so that there would be a transitory period during the transfer operation where both of the tanks were communicated with valve return ports. If one of the pair of tanks was filled, the return fuel flow from the carburetor could cause fuel overfill from the tank.
Relevant prior art includes U.S. Pat. No. 2,557,438 issued June 19, 1951 to Johnson showing multiple fuel tank transfer system having solenoid operated, air controllable valves. This system is costly and slow to respond and is not readily adapted for use in mass-produced vehicular fuel tank systems.
U.S. Pat. No. 3,916,938 issued Nov. 4, 1975 to Hack shows an emergency fuel tank transfer system for use on vehicles. It does not include a double shuttle type valve with flow control, and return of unused fuel from a carburetor.
U.S. Pat. No. 4,128,113 issued Dec. 5, 1978 to Hart shows a dual poppet type shuttle valve for use in fluid systems. It requires valve plugs with a ring packing which increases its cost of manufacture and complicates the valve operation. Furthermore, it does not suggest an arrangement for inclusion of plural ones of double shuttle valve plug units in a dual tank truck application.
A fuel recirculating system is set forth in U.S. Pat. No. 2,672,189 issued Mar. 16, 1954 to Welsh. It includes manually operated plug type rotary control valves to select the fuel path from the fuel pump to the carburetor or to select a path from the auxiliary fuel tank 10 back to the carburetor. It does not include any of the component parts or operating principles of the valve of the present invention.
U.S. Pat. Nos. 2,060,735 and 3,332,440 issued Nov. 10, 1936 to Krueger and on July 25, 1967 to Brakebill, respectively, show solid stem double shuttle valve systems for regulating fluid flow between multiple inlets and outlets of a valving structure. Otherwise they do not pertain to the present invention.